To evaluate three types of ventilation systems for operating rooms with respect to air cleanliness [in colony-forming units (cfu/m³)], energy consumption and comfort of working environment (noise and draught) as reported by surgical team members.

Two commonly used ventilation systems, vertical laminar airflow (LAF) and turbulent mixed airflow (TMA), were compared with a newly developed ventilation technique, temperature-controlled airflow (T_cAF). The cfu concentrations were measured at three locations in an operating room during 45 orthopaedic procedures: close to the wound (<40cm), at the instrument table and peripherally in the room. The operating team evaluated the comfort of the working environment by answering a questionnaire.

LAF and T_cAF, but not TMA, resulted in less than 10cfu/m³ at all measurement locations in the room during surgery. Median values of cfu/m³ close to the wound (250 samples) were 0 for LAF, 1 for T_cAF and 10 for TMA. Peripherally in the room, the cfu concentrations were lowest for T_cAF. The cfu concentrations did not scale proportionally with airflow rates. Compared with LAF, the power consumption of T_cAF was 28% lower and there was significantly less disturbance from noise and draught.

T_cAF and LAF remove bacteria more efficiently from the air than TMA, especially close to the wound and at the instrument table. Like LAF, the new T_cAF ventilation system maintained very low levels of cfu in the air, but T_cAF used substantially less energy and provided a more comfortable working environment than LAF. This enables energy savings with preserved air quality.